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6697236: missing Identity for "(X+Y) - X" into Y

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Reviewed-by: kvn
This commit is contained in:
Tom Rodriguez 2008-06-12 09:47:55 -07:00
parent 01130cd21c
commit b381148ebe
1 changed files with 4 additions and 1 deletions
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5
hotspot/src/share/vm/opto/subnode.cpp
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@ -45,10 +45,13 @@ Node *SubNode::Identity( PhaseTransform *phase ) {
return in(2)->in(2);
}
// Convert "(X+Y) - Y" into X
// Convert "(X+Y) - Y" into X and "(X+Y) - X" into Y
if( in(1)->Opcode() == Op_AddI ) {
if( phase->eqv(in(1)->in(2),in(2)) )
return in(1)->in(1);
if (phase->eqv(in(1)->in(1),in(2)))
return in(1)->in(2);
// Also catch: "(X + Opaque2(Y)) - Y". In this case, 'Y' is a loop-varying
// trip counter and X is likely to be loop-invariant (that's how O2 Nodes
// are originally used, although the optimizer sometimes jiggers things).